The pending Supreme Court case, South Dakota versus Wayfair (W), could be a "sneaky positive" for Best Buy (BBY) should the Supreme Court rule in favor of South Dakota, Piper Jaffray analyst Peter Keith tells investors in a research note. A rule in favor of South Dakota, which the analyst expects, would allow states to start collecting sales tax on e-commerce purchases. Sales tax has become less of a factor for purchasing decisions, but it still matters for big-ticket, branded items, Keith contends. He reiterates an Overweight rating on Best Buy with an $89 price target.